GEOLOGY OF THE NORTH CREEK QUADR ANCLE 59 



hornblende granite. At times the rock is pinkish gray, medium to 

 coarse grained, and not very gneissoid ; while again, and by rapid 

 changes, the rock is gray, fine grained, and very gneissoid to al- 

 most schistose. Both rock types have the same composition and 

 both show signs of granulation, but the latter rock especially so. 

 One of these clearly does not cut the other, but rather there is a 

 rapid gradation from one to the other parallel to the foliation, 

 and it seems clear that the fine grained, very gneissoid rocks were 

 produced along belts of shearing perhaps at the time of the de- 

 velopment of the foliation. Such a rapid transition from fine to 

 medium grained granite is also well shown even in a hand speci- 

 men from the summit of Oven mountain. 



Many dip and strike observations on the foliation were made, 

 the more representative ones being plotted on the accompanying 

 map. Strike observations can generally be made with a fair degree 

 of accuracy, but dips can seldom be determined to nearer than 5 

 or 10 degrees. The amount of dip is usually rather moderate, most 

 often ranging from 30 to 60 degrees. Considered as a whole, the 

 prevailing strike of the foliation ranges from north and south 

 to northwest and southeast with dips almost uniformly toward 

 the east. The northern central portion is exceptional with its east 

 and west strike and northward dip. Also there are important 

 departures from the prevailing direction of dip and strike in cer- 

 tain Grenville areas as south of Johnsburg, south of Thurman, and 

 between Pottersville and Starbuckville, in which areas the direc- 

 tions are very variable. On the Long lake sheet, according to 

 Professor Gushing, the foliation is more erratic in the eruptives 

 than in the Grenville, but here precisely the reverse is true. 



FOLDING 



Before any important general statements can be made regard- 

 ing the character of the folding, a wider area will have to be 

 studied. A striking feature is the almost uniform eastward to 

 northeastward dip of the foliation, which suggests the possibility 

 of isoclinal folding but aside from this uniform direction of dip, 

 there is much evidence against such isoclinal folding. The gen- 

 erally moderate angles of dip; the perfect agreement of foliation 

 and bedding planes even where the strikes and dips are erratic ; 

 and the utter lack of any evidence for repetition of the strata even 

 in long sections like that of figure i are strong points against 

 isoclinal folding. Professors Gushing and Kemp recently stated 



